Exploration of trajectories of expressive language samples is essential for understanding potential indicators for language disorder assessment. This study examined conversational language samples from 341 typically developing Mandarin-speaking children aged 3–7. Through analysis of lexical diversity and word classes, a norm-referenced dataset for vocabulary assessment was built, including indicators such as vocD and the types and tokens of nouns, verbs, measures, adverbs, conjunctions and prepositions. As norm-referenced indicators for the language development of children speaking Mandarin, these developmental data could also inform clinical therapists about the direction of intervention for children with vocabulary deficits.